This invention relates to fastening devices and, more particularly, to multi-function, integrally molded, plastic fasteners which function in hollow, thick or solid support members such as walls or partitions.
Multi-function plastic expansible fasteners of the type disclosed in U.S. Pat. No. 3,651,734, issued to one of the inventors herein on Mar. 28, 1972, have attained wide-ranging commercial success throughout the world. This fastener can act as a wedge in a solid wall and also has the capability of opening, upon insertion through a hollow wall, to provide a positive blind side anchorage so that it can reliably function in this mode as well. Modifications of fasteners, as disclosed in U.S. Pat. No. 4,181,061, issued to the same inventor on Jan. 1, 1980, have tended to be more limited in their application. For example, in this latter patent, an integrally molded plastic fastener is disclosed with enhanced load bearing capability but is described as being specifically for use in hollow walls. Dowel fasteners, for example as described in U.S. Pat. Nos. 4,142,440, and 4,518,291, issued Mar. 6, 1979 and May 21, 1985 respectively, represent other types of fasteners which are exclusively for use in solid wall applications.
With the embodiments disclosed in the aforementioned patents, as well as with many other wall fasteners, a hole, of sufficient width to permit passage of the anchoring element portion of the fastener, is initially formed in a support member such as a wall. The anchoring element of the fastener is then inserted therethrough for fixed deployment of the fastener. It is highly desirable to minimize passage hole width to (in addition to aesthetic considerations) reduce any possible damage to walls, to facilitate drilling particularly in hard structures such as masonry or concrete and to reduce areal fill-ins should the fasteners be removed. Accordingly, many fastening devices, particularly those designed for utilization in hollow wall applications, are specifically designed to permit temporary folding or collapsing of the anchoring elements of the fasteners to reduce the size required for the passage hole. Attempts to actually reduce the dimension of the anchoring elements to concomitantly further reduce hole size have generally only resulted in reduction of the load bearing capability of such fasteners.
It is an object of the present invention to provide a multi-function fastening device utilizable in hollow, thick or solid walls with passage holes of reduced dimension, while having substantially equivalent or enhanced load bearing capability as compared to fasteners requiring larger passage holes.
It is a further object of the present invention to provide a multiple application high strength fastening device which is capable of being installed on an automated basis.
These and other objects, features and advantages of the present invention will become more apparent from the following discussion as well as the drawings in which: